I have a copy of the Tamron 20-40 and it is a great lens. Good luck with your sale, I'm sure whoever buys it will like it as much as I do Mine.
Mike
I shot similar subjects, and although it only has 11 autofocus point, I don't find this is a disadvantage, but a positive. My screen on the 1d I have is filled with autofocus points, and I find that to be more of a distraction then a positive. The 6d focus points seem to be just were I need them and they don't clutter up the viewfinder. It has a very similar look to my 50d. I would also highly recommend the 6d for the type of subjects you shoot. Locking focus is not as important with your subject matter, and I find the low light focusing is Great for my architectural shots. Although the 6d only has a center cross type focus point, I find I generally use the center point and focus and recompose, so again this is not a limitation for me.
I recently purchased a refurbished Canon G1x from canon for a much discounted price, It is not what I call a super zoom, it has a 28-112 zoom range, but almost a full crop sensor, so the images it produces are of a very high quality. It is not super small or lightweight, but it is much lighter then taking your dslr. I think it is the perfect combination of size, image quality and features.
I have had great luck with used lenses from them. I ordered a 80-200mm Tokina lens and after 5 months the manual to auto focus clutch stopped working and they took it back and gave me full credit, with which I purchased a canon 80-200 L lens, they indicated that it was in Fair condition, but I rated it much higher then they did. Other lens I purchased from them have been wonderful.
I have a tripod which allow the head to be adjusted but I have started to use a manfrotto Magic Arm attached to the bottom of the center column on my heavier tripod. I find this setup to be much quicker to adjust then the adjustable head. It allows unlimited freedom to adjust the camera close to the ground to shoot vertical or horizontal.
If money is no object you might want to look at Canon EF 11-24mm f/4L USM Wide Angle Zoom Lens at $2999 this is both very expensive and has been getting reviews as being one of the best ultra wide angle lens by any manufacture. It also has the advantage of working on both crop and full frame bodies and it's a L lens.
Just to give you another option the Tamron SP 70-300mm F/4-5.6 Di VC USD has proved to be a great lens with great IS. I decided to purchase it instead of the 70-300 is and have been very happy with my selection. It is not up to the level of the L lens but it compares very nicely next to the 70-300is lens.
I bought the same lens for the same reason, I have found it to be, a nice lens to use it is much lighter then the other lenses of the same size, it light enough to hand held at an air show, with faster shutter speed. I did find it it has some chromatic aberation on the chrome plains, but is very minor in regular landscape photos. I also like the feature which allow rotation of the polerizer even with the lens hood on.
If the lens is an older tokina lens, it may be similar to the older sigma lens and just not be compatible with the new eos cameras. If it was designed for thet eos film cameras it is likely not to work with your digital camera. In the future when purchasing either sigma or tokina, make sure it is listed for digital and not just film.
I might suggest another option, rather then dvd's you might look into joining Kelby One. With the membership you get access to streaming video covering from the basic to the advances, the price varies from around two hundred to two hundred and fifty, depending on the specials they are running. They also cover photoshop and lightroom. I found this was the best money I sent when I got back into photography. I also have the Karl Taylor dvd's which are also excelant, but not as diverse as Kelby One.
I started out with full frame about 18 months ago with the 5d. I find it gives very good images, but it is limited to lower iso's. I have since upgraded to a 6d. I love both cameras. The limitations I found with the 5d is a lower grade rear screen and the lack of automatic sensor cleaning. I found that i had to do a a regular manual sensor cleaning to keep my pictures clean. The 5d, even at 12.8mp, does have a quality about the images, that I don't get from any of my other cameras. I fined that I still use it when I don't need the high iso or large image sizes, such as the landscape pictures. Comparing the images from my 6d and 5d, the 6d is great for low light and high iso, from my readings I think the 5dmark II falls somewhere in the middle, better then the 5d, but not in the same class as the 6d or 5d mark iii with respect to high iso.
I would suggest the 18-135 it is rated as sharper then the 18-200 and gives your the approximate range of 28-200 with the 1.6 conversion factor. I have both this lens and the 18-55, both with IS and find the 18-135 a much better walk around lens.
Just be carful that the hood will fit on with the larger filter size. I'm not sure about 70-200.
I also have both the 60d and 6d and find they are a great combination. They use the same batteries, area about the same size and the controls are laid out in a very similar manor. I also have a 5d and 50d which I also use in combination for the same reason, batteries and controls.
The combination of the 6d and 60d is my preferred technique rather than s teleconverter. I use the 60d as a 1.6 teleconverter without any loss in f stops.